This reminded me of Black Ops during that mission on the mountains with Hudson.

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It's Nitori with an AUG. I shouldn't be thinking too deeply into this.

Reewee said:
Well its not in the pixiv tags, but I would say more likely than not he drew influence from that one particular mission, taking into consideration the majority of artist's works is composed of call of duty fan art.

Could be from the winter missions in MW2, random mooks could drop an AUG from time to time.